triclinic Tectosilicates
Labradorite
(Ca,Na)(Al,Si)4O8
Crystal Structure
triclinic[-1]:{010}@1.0 + {001}@0.8 + {110}@0.6 | phenomenon[labradorescence] triclinic
-1
{010} {001} {110}
Quick Facts
Hardness
6.0
Specific Gravity
2.69
Refractive Index
1.559
Optical Character
Biaxial +
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Open in PlaygroundPhysical Properties
Crystal Systemtriclinic
Hardness (Mohs)6.0
Specific Gravity2.69
CleavagePerfect in two directions at ~90 degrees
FractureUneven to conchoidal
LustreVitreous to pearly
Optical Properties
Refractive Index1.559
Birefringence0.008-0.010
Optical CharacterBiaxial +
Dispersion0.012
PleochroismNone to weak
PhenomenonLabradorescence
Colours
Grey body with blue flashGrey body with green flashGrey body with gold flashGrey body with purple flashSpectral colours (Spectrolite)Rainbow flashes
Localities
MadagascarCanada (Labrador - type locality)Finland (Spectrolite)MexicoRussiaAustralia
Common Inclusions
Twin lamellae (cause of phenomenon)Exsolution lamellaeMagnetite inclusionsGrowth features
Known Treatments
Generally not treated
Crystal Forms
pinacoidprism
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Open in PlaygroundRelated Minerals
Other minerals in the triclinic system
